1. Field of the Invention
The present invention relates to a captive washer, and more particularly to a captive washer that adjusts tension of a drum and reduces vibration of the drum.
2. Description of Related Art
With reference to FIGS. 4 and 5, a conventional drum normally comprises a cylindrical drum shell (50), multiple tension control devices (60), two annular drum hoops (52) and two drumheads (51). The cylindrical drum shell (50) includes two round openings and a sidewall. The tension control devices (60) are mounted on the sidewall of the drum shell (50). The annular drum hoops (52) are mounted respectively on the two openings, and each drum hoop (52) has multiple elongated holes (520). The elongated holes (520) are elongated circumferentially, are formed through the annular drum hoops (52) and align respectively with the tension control devices (60). The drumheads (51) are mounted respectively in the annular drum hoops (52), cover the two openings, are made of leather or similar resilient material and have a tension. The tension of the drumheads (51) determines a drum's tone and is controlled by the tension control devices (60) drawing the drum hoops (52) closer together to increase the tension of the drumheads (51).
With further reference to FIG. 6, a conventional tension control device (60) has a mounting post (62), a connector (63), two washers (65) and two adjusting bolts (61). The mounting post (62) is attached to and protrudes out radially from the sidewall of the shell (50) and has a proximal end, a distal end and a mounting hole. The proximal end of the mounting post (62) is attached securely to sidewall of the drum shell (50), and the mounting hole is formed transversely through the mounting post (62) near the distal end. The connector (63) is tubular and is mounted slidably through the mounting hole and has two ends, an attachment hole (631) and an internal thread. The ends are opposite to each other. The attachment hole (631) extends axially through the connector (63), and the internal thread is defined longitudinally in the connector (63). The washers (65) press respectively against the drum hoops (52) at the elongated holes (520), and each washer (65) has a through hole (651). The through hole (651) is formed through the washer (65) and communicates with the elongated hole (520). The adjusting bolts (61) are mounted respectively through the through holes (651) in the washers (65) and two corresponding elongated holes (520) respectively in the drum hoops (52) and are screwed respectively into opposite ends of the connector (63). Each adjusting bolt (61) has a proximal end, a distal end, a flange and a thread. The flange is formed near the distal end of the adjusting bolt (61) and presses against the washer (65). The proximal ends of the adjusting bolts (61) are screwed respectively into the ends of the connector (63) to adjust the distance between the drum hoops (52) and the tension on the drumheads (51).
However, defects and restrictions of conventional washers (65) of tension control devices (60) for a drum follow.
1. The washers (65) being mounted between the flanges of the adjusting bolts (61) and the elongated holes (520) of the drum hoops (52) absorb vibration from the drum hoops (52). However, the adjusting bolts (61) press against the elongated holes (520) opposite to the washers (65), which causes the vibration between the adjusting bolts (61) and the elongated holes (520) of the drum hoops (52) to loosen the adjusting bolts (61) from the connector (63). Consequently, the tone of the drumheads (51) change while the drum is played.
2. Changing the drumheads (51) necessitates removal of the adjusting bolts (61) from the connector (63) of the tension control device (60) and the elongated holes (520) in the corresponding drum hoop (52). Consequently, the washers (65) may be lost in the process, which would be very inconvenient and could keep the drum from being used unless a replacement washer was available.
Therefore, the invention provides a captive washer to mitigate or obviate the aforementioned problems.